Humanized antibodies can be used as therapeutic agents in place of murine antibodies to avoid the undesirable immune response in humans termed the HAMA (Human Anti-Mouse Antibody) response. Humanized antibodies are generally constructed by replacing the complementary determining regions (CDRs) of a human antibody with the CDRs of another species, typically a mouse antibody.
VLA-4 (also called α4β1) is a member of the β1 integrin family of cell surface receptors. VLA-4 contains an α4 chain and a β1 chain and is involved in cell-cell interactions. Its expression is mainly restricted to lymphoid and myeloid cells. VLA-4 binds the endothelial cell ligand VCAM-1 (Vascular Cell Adhesion Molecule-1), and can mediate T and B lymphocyte attachment to the heparin II binding fragment of human plasma fibronectin.